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(No M6881.) A8 sheets-sheet 1.

.T. S. E. DIXON.4

AIR BRAKE.

No. 882,081. Patented May 1, 1888.

(No Mmm.) s sheets-sheet 2..

- T. S. E. DIXON.

, AIR BRAKE. No. 382,031. Patented May 1. 1888.

F/'yae. 2.

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(No Model.) 3 Sheets-Sheet 3..

T. S. E. DIXON.

A111 BRAKE.

No. 882,081. Patented May 1, 1888.

UNITED STATES PATENT Ori-ICEo THERON S. E. DIXON, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO Y LYSANDER HILL, OF SAME PLACE.

AIR-BRAKE.. I

SPECIFICATION forming part of Letters Patent No. 382,031, dated May 1, 1888.

Application filed Dicfmber 16, 1887. Serial No. 2549x111. (No model.)

To LZZ whom it may concern.-

Be it known that I, THERON S.` E. DIXON, a citizen of the United States of America, residing at Ghicago,in the county ofOook and State of Illinois,have invented certain new and useful Improvements in Air-Brakes,of which the following is a specification.

In allso-called automatic air-brakes heretofore known, so far as I am aware, in which the admission of compressed air to the brakecylinder and its discharge therefrom are governed by a sliding piston which is actuated by varyingthe air-pressure in a train-pipe leading from the locomotive, and which controls the admission of air to the brake-cylinder from a separate storage-reservoir under each car, said piston has always been subjected to a variable pressure at both of its ends-a mode of operation that renders its action more or less uncertain and unreliable under many con ditions of use.

In the following specification, for convenience of description, I shall term that end of the piston against which the air from the trainpipe acts the outer end, and its opposite extremity the inner end, and shall speak of its traverse as outward when moving in a direction from its inner toward its outer end and as inward when moving in the reverse direction. u

One ofthe main objects of my invention is to obviate the practical defect above referred to by subjecting the inner end of the piston to a constant normal pressure which is substantially uniform throughout its entire traverse, so that when the air-pressurein the trainpipe Ais raised and maintained above a predetermined degree the piston will move inward to the end ofits traverse, and when reduced and held below such degree the piston, unless arrested by independent stops, will move out` ward to the end of its traversea mode of operation entirely new, so far as I am aware, in air-brakes having a separate storage reservoir attached to each car, and which constitutes one of the main principles of my invention. In the preferred form of apparatus herein shown and described I obtain the constant pressure referred to from the back action of the compressed aircontained in an auxiliary storagereservoir communicating withthe inner end of the piston and of such capacity as to produce v a substantially uniform pressure thereon throughout its traverse, said auxiliary reservoir not being used for ordinary service-stops and grading the speed of the train, and therefore not Subj ect to tluctuatio ns of pressure during the traverse of the piston.

Another independent and important principle of my invention consists in the employ- 6o ment of a series of graduated yielding resistances or stops for the purpose of arresting the movement of the piston at different points along its traverse, in order that it may open and hold open,` or close and hold closed, the several ports at the will of the engineer and upon his bringing the train-pipe air to a predetermined and foreknown degree of pressure corresponding to each of said resistances.

Another independent and important princi- 7c ple of my invention consists in employing a series of car-reservoirs,some of which are caused 'to communicate with the brake-cylinder when said piston is at one position and others when it is at other positions, the main objectof this part of my invention being to provide for the purpose of emergency-Stops 7 an independent source of compressed air not liable to depletion by service-stops or grading#7 but always full to its maximum capacity and ready 8o for instant and effective use in case of any emergency.

Another independent and important principle of my invention consists in arranging the discharge-port of the brake-cylinder so that it will be opened and the brakes released when the valve-piston aforesaid is at some intermediate position between the eXtreme ends of its traverse, and not when it is at the inner end of its traverse, as heretofore; and anotherim- 9o portant principle of my invention consists in providing means whereby a Apiston constructed to release the brakes when it is at intermediate points of its traverse, as aforesaid,` can at any time, if desired, be readily caused 9'5 to release-the brakes when at the inner end of its traverse, instead of releasing them when at said intermediate points, and can afterward be as readily converted back to its original mode of operation.

Subordinateimprovements are found in the various devices and combinations more particularly specified in certain of my claims hereto appended.

The broad principles of my invention above stated are capable of practical embodiment in a variety of apparatus, of which one form is illustrated in the drawings. The structure therein shown is simple, durable, and not liable to get out of order. Its operation is such that at any time, by a most simple manipulation ofthe air-cock on the locomotive, any desireddegree of air-pressure can be admitted from the serviecreservoir to the brake-cylinder, and can then be as readily increased or decreased at the will of the engineer without releasing the brakes, the apparatus being as perfectly controllable in that respect as the electric air-brake. Vhenever the trainpipe is emptied for an emergency, the maximum pressure is behind the piston to force it out and insure its action, and the maximum reservoir-pressure is always present to enter the brake-cylinder and set the brakes. rllhe various reservoirs can be refilled whether the brakes are on or oft at the time.

A car containing the invention can at any time, by simply turning a cock, be adapted to work in the same train with other cars containing the old forms of air-brakes.

Having thus stated the general principles, mode of operation, and practical advantages of my improvements, I will now proceed to particularly describe one form of apparatus in which they are all embodied, making reference,for purposes of illustration, to the accompanying drawings, in which- Figure l is a vertical section of my valve device; Fig. 2, a horizontal section (looking upward) in line 2 2 of Fig. l; Figs. 3, 4, plans of the valvesurt'acc, showing the two alternative arrangements of the service and release ports herein described; and Fig. 5, a. perspective view of the entire apparatus when appropriately arranged for service under a ear.

Referring to said drawings, in which similar letters of reference indicate like parts, A is the traiirpipe; B, the brakecylinder; C, the ordinary servicereservoir, and D the valvepiston provided with a valve surface, E, whose movements open and close the several ports. rlhe piston is arranged in a suitable casing, F, connected to the train-pipe by a passage, G, to the service-reservoir by a passage, H, to the brake-cylinder by a passage, l, to an auxiliary air-reservoir, K, by a passage, J, or an opening in the wall of such reservoir, and to the atmosphere by a passage, M. The valve-piston and its accessories may be widely varied in structure without departing from the principles of my invention. In the preferable form herein shown said piston is made hollow and contains two sliding members having different ranges of movement and held normally in' position in the piston by two springs. One of the sliding members is preferably in the form of a ring (marked l) which seats against ton, or a suitable shoulder of the latter, by a spring, S. The piston itself, under the action of alight spring. S, normally stands in the position shown in Fig. l, with the air-pressure of the reservoir K acting against its inner end and the airpressure from the train-pipe acting against its outer end. When the train-pipe pressure is reduced a few pounds, the pressure of the compressed air in the auxiliary reservoir K, overcoming the resistance ofthe light spring S, will move the piston outward till the stem 4 strikes the end wall of the easing atf, whereupon its movement will be arrested, and it will remain in that position so long as the train-pipepressure remains unchanged. Upon decreasing the train-pipe pressure, however, until the excess of pressure at the inner end of the piston is sufficient to overcome the combined resistance of the springs S S', the piston will move outward still farther until thehead or block 3 strikes against the ring l and again arrests its movement. Upon further reducing the train-pipe pressure until the excess of pressure at the inner end of the piston is stiflicient to overcome the combined resistance of the three springs S S S", the piston will move outward to the limit of its traverse. Then, conversely, upon restoring the train-pipe pressure to such a degree that, in combination with the three springs S S S2, it is able to overcome the resistance ofthe air from reservoir K, the piston will return tothe point where the spring S'l ceases to act, and will stop there. Upon further increasing the trainvpipcrpressure until, in combination with the two springs S S, it is able to overcome the resistance from reservoir K, the piston will continue its retrograde movement to the point where the spring S ceases to act, and will stop there, and upon further increasing the train pipe pressure until, in combination with the spring S alone, it is able to overcome the resistance from reservoir K, the piston will return to its normal position. The piston thus moves in each direction step by step to predetermined and fixed positions by the discharge or admission of predetermined amounts of airpressure through the train-pipe, and its position at any time is manifest to the engineer by a glance at his trainpipe pressuregage.

An incidental improvement consists in reversing the usual position of the piston and casing, so as to connect the trai n-pipe to their upper end and the reservoir K to their lower end, whereby the weight of the piston tends to bring it to and keep it in its normal position at the inner end of its traverse and to prevent it from being jarred out of such position by the movements of the ear, and whereby, by suitably weighting the piston, the spring S may be dispensed with, if preferred, and whereby the usual plugged drip-cup is enabled to be lOO IID

ISO

dispensed with,as all drainage will flow through the pipe J into the reservoir K, whence it can be drawn oft' through the usual bleeding-cock.V

The relative force of the springs S S S2 or the springs S S2 and weight may be graduated and xed as the constructors experience shall approve; but it is best to so graduate it that a preliminary change of' several pounds in the train-pipe air-pressu re shall be required to effeet each separate step in the movement of the piston, thereby allowing several degrees of latitude for differences in the friction of different valves and for carelessness or inattention on the part of the engineer. I recommend such a graduation that a reduction of fve eighths of a pound in the trainpipe pressure will lnove the piston from its normal position to its first stop, ve-eighths Vof a pound further reduction will move it to its second stop, and iveeighths of a pound further reduction will move it to the outer limit ef its traverse; but these proportions may be varied, if preferred. Anycompetentarrangementofsprings or their equivalents to arrest the traverse of the piston at its several predetermined points, as aforesaid, may be adopted instead of the particular construction here shown, the latter being only a4 preferable form adapted to the use of long, and therefore comparatively equable, springs in a comparatively compact structure. A modification which has some merit consists in extending the spring S only from 'the outer end of the casing F to some partpreferably the inner end-of the stem 4.

In Fig. 1 dotted lines at n indicate that the tubular stein is closed at its inner end, and that the spring S, adapted to this modified construction,'terminates at the closed end of the stem. The advantage of this modified con` struction is that from the moment when the stem 4 strikes the casing at f until it again separates therefrom theresistance of the spring S to the movements of the piston is absolutely uniform, because the spring can be compressed no farther. Itis obvious that the same principle may beappliedinoonnection with thespring S. If these springs are made of cast-steel, nickelplated in the rough, they will endure for years without change of tension.

Those features of my invention hereinabove particularly described are independent of any specific arrangement of the parts controlled by the pistonvalve. The reservoirs, however, are preferably refilled when the piston is at its normal position. To this end I arrange in the wall of the casing a passage, h, (dotted'lines, Fig. 1,) extending from the space at the outer end of the piston to and through the inner Wall of the casing at a point near the end of the passage H, which leads to the servicereservoir, and provide in the side of the valve surface E a refilling-port or bypass, e, which, when the piston is at its normal position, puts the passages H h into commu nication with each other, as shown in Figs. 3, 4, and enables the reservoir to be filled or refilled from the trainpipe to the maximum pressureA desired. The

independent reservoir K may be filled in any appropriate manner-for example, by a passage, c, leading from the service-reservoir C- and. provided with a check-valve, c', Vseating backward, as shown in Fig. 5. If the checkvalve c be loaded one or two pounds to the square inch, it will produce the same eect as the spring S on the piston D, and will be a practical equivalent therefor. The automatic or emergency stop port E3, which communicates with the passage J by a hole in the piston, (shown in dotted lines at j, Fig. 1,) is arranged, as usual, to put the appropriate storage-reservoir into communication with the brake-cylinder when t-he piston has arrived at or nearly at the outer extremity of its traverse.

I contemplate two different arrangements of the service port or by-pass ez and brake-release port or by-pass e', as shown, respectively, in Figs. 3 and 4C.

In Fig. 3 (the preferred form) the brake-release port e puts the passage I into communication with the passage M, leading to the atmosphere, and thereby releases the brakes when the piston arrives at the first stop in its outward traverse, and the serviceport e2 puts the passages H I into communication with each other, and thereby applies the brakes for service-stops or grading when the piston reaches its second stop. Vith this arrangement the piston may be moved to its second stop and t-he brakes thereby applied with any desired force, depending upon the length of time itis held there; and it may then, at will, be either moved back to its rst stop and retained there long enough to wholly or partially release the brakes, or, by suddenly increasing the trainpipe pressure to the maximum, it may be shot back'from its second stop to its normal posi tion so quickly as not to release the brakes, and then the reservoirs may be refilled with the brakes set.

In Fig. 4 the release-port e' is arranged to put the passages I M into communication and thus release the brakes when the piston is at its normal position, and the service-port e2 is arranged to' open communication from H to I when the piston arrives at its first stop. With this arrangement the engineer can, by moving the piston to its first stop, apply the brakes with any degree of pressure desired, depend ing, as before, upon the length of time it is held there, and he can then, by moving it to its second stop, hold the brakes so set, or by moving it back to its normal position ,release them and retill his reservoir. With either arrangement the piston can be moved back and forth Abetween the serviceport and the releaseport as often as desircd,and held at either port as long as desired; and hence for servicestops or grading speed the brakes can be applied and their pressure increased, reduced, or discharged altogether, at the will of the engineer, and by thesimplest manipulation of the pressure-controlling cock ou the engine, the train-pipe pressure-gage always showing exactly where the piston is and what to do IIO i segnet4 with it next for any purpose required. The serviceport and release-port being made of the proper size, the amount of reservoir airpressure vented into the brake-cylinder or discharged therefrom will always depend upon the length of' time that the respective ports are held open, in which respect the operation of my pneumatic system is superior to that of the electric airbrake, giving as ready and more perfect control of the brake-pressure for service and grading purposes, without that liability to accidental derangement which necessarily attends the use of electric connections and devices, and without the expense and care of electric appliances.

It will be observed that in Fig. 3 the valve is adapted to wholly or partially release the brakes when the piston is in an intermediate position between the extreme ends of' its f' traverse. This I regard as an important impiovement in the art, in that it enables the brakes to be held under moderate pressure in grading,7 and the reservoirs to be refilled without releasing the brakes when set. Cars provided with this improvement are liable,

` the release-port e when the piston is at the eX- treme inner end of its traverse, and I extend the ports M M' through two cocks, or, preferably, through a two-way cock, m, which,

when turned to oneposition, opens the escapepassage M and closes M', and when turned to another position opens h' and closes M, thus putting either of the openeair ports at will under the control of the piston and excluding the other.

' In connection with or independently of the abovedescribed improvements I provide each car with a series of two or more reservoirs in order that I may draw the air from one of saidV reservoirs, C, for the purposes of service-stops and grading without interfering with the air reserved in another reservoir, K, for the purpose of emergencystops. To this end the reservoir Kis out off from all communication with the serviceport chaud only communicates with the brakecylinder through the emergency port e3, while the service-reservoir C is cut off' from all direct communication with the emergency-port. Vith this construction, and using the emergency-reservoir to furnish the airpressure against the inner end of the piston, it results that while such pressure is not liable to variation during the traverse of/the piston, yet the application of the emergency-stop, which involves a considerable preliminary reduction of train-pipe pressure, is followed, at the outer end of such traverse, by a consequent reduction of the resistance at the inner end i the piston rtoinsure its proper working.

of the piston through the discharge of air from reservoir K to the brake-cylinder, and therefore the piston is able to be more readily and quickly returned to the releaseport or refilling-port.

Another advantage which arises from filling the emergency-reservoir from the service-reservoir hy-means of the passage C and checkvalve c is, that although the depletion of the reservoir C for service-stops or grading will not affect the contents of the emergency-reservoir, yet the opening of the .emergency-port will vent air from bot-h of said reservoirs to the brakecylinder, andthe increased air capacity, when fillcd,thus obtained for emergency purposes will enable the brakes to he set with Y greater force than would otherwise be attainable. The air from reservoir K can, under no circumstances, get back to the train-pipc. Even if the piston should stick at its normal position from some accidental cause and allow the contents of the service-reservoir to vent back through the passage H e h thc chockvalve o will prevent any depletion ofthe reservoir K, thus insuring certainty in the movement of the piston. I prefer to make the pis ton D about three inches in diameter, giving a transverse sectional area of about seven square inches. With the ordinary reservoir pressure of sixty pounds per square inch, therefore,` I have over i'our hundred pounds of air-pressure available against the inner end of' `The initial pressure is sixty pounds to the square inch, and, if the reservoir K is made of suitable size, the diminution ofthispressurewhich results from the outward movement of the piston will be practically inconsequential.

It should be remembered that by suddenly emptying or refilling the train-pipe the piston can be shot from one end of' its traverse to the other, in either direction without practically bringing the intermediate parts into operation, and hence, whether the brakes be set by air from the service-port or from the emergency-port, the piston, in the form shown in Fig. 3, can be returned to its normal position andthe reservoirs refilled without releasing them. It is well known that by proper attention to his pressure-gage and air-cock the engineer can govern the pressure in the trainpipe to within the fraction of a pound. The piston is therefore perfectly under his control. He can move it to open theservice-port and apply any brake-pressure desired. Then, if he desires to reduce such brake-pressure, he can move it back to the release-port and discharge the pressure more or less at will. If he then needs more brake-pressure, he can sendit back to the service-port and apply such increase. If he desires to hold the brakes under a medium pressure without changefor example, down a long grade-he can return it to its normal position for that purpose, when he can also refill his service-reservoir. If he needs the full emergency pressure,he can use it at any moment.

In a word, he can hans.

dle the piston-valve just as he may desire, whether for emergency-stops, service-stops, grading thespeed ofthatrain, releasing brakes, or reiilling his reservoirs. No complicated manipulation of the engineers cock is required, a simple movement, indicated by the reading of the pressure-gage, being all that is necessary to effect any of these results. The air for service-stops and grading being applied from the reservoir C, and the air for emergencystops being derived from an independent reservoir, the depletion of the former never affects or diminishes the full pressure of thelatter, which is always ready` with its entire reserved force for any contingency. If the engineer should by inattention or accident increase or reduce his train-pipe pressure several pounds more than is necessary to effect any movement desired by him, the result will be the precise movement requiredin fact, in

. ordinary practice, he will so increase or reduce it a pound or two more than is necessary in order to allow for differences of friction among' the different valves and to insure the exact result desired. Only by not venting enough or by carelessly venting atleast about double the amount necessary can he fail to produce this result. It will be observed that normally the airpressure against the opposite ends of the piston is equal, and hence there is no danger of leakage around it. To guard against any temporary leakage when the train-'pipe pressure is reduced, or when after emergencystops `the pressure of reservoir K is reduced, the piston should be suitably packed air-tight inits casing. Inasmuch as this packing passes no air-ports or bypass,any ordinary meanssuch asrubber, leather,or ring packingmay be employed. I have devised a very simple and etcientleather packing for the purpose, as follows: I construct the outer head of the piston in a separate piece, d, provided with a neck, d', which screws into the interior of the piston and forms the stop for thering 1. I bevel or curve the proximate outer edges of the piston D and its head d, as shown at did", to accommodate leather rings d4 d5, held between the piston and head, with their outer edges overlapping,

said beveled corners. Between the two leather rings I preferably place an annular disk, d, of metal or some iigid substance. Springrings d7 may also be inserted to aid in holding the leathers to their seat. When the head is screwed into the piston, it binds all these packing-rings securely in place and causes the joint to be eii'ectively packed against leakage. The fact that the piston-packing passes by no port, by-pass, or other opening in the wall of the casing not only enables me to use soft packing*such as leather, &c.,which is well known to give the best protection against air-leakage but prevents the possibility of any air escaping back from the reservoir K to the trainpipe through any such port or by-pass in ca se the valve or piston should accidentally stick' at any point in its traverse, and thus insures the proper movement of the piston under all circumstances.

The valve-surface E is preferably made in the old and well-known form of a block or plate fitted into a recess in the side of the piston and held to its seat by a spring or by the pressure of air admitted behind it through the space or passage j.

The ordinary air-pump, locomotive-reservoir, pressure-gages, and engineers controlling cock or cocks may be employed, as in the old systems, no change of the apparatus connected with the locomotive being necessary to adapt it to the use of my inventions. The employment of a flexible diaphragm as an equivvaient for a sliding piston to control the movements of a valve is too well known in the art to require description here.

The two great advantages of my improvements asV a whole are, first, that they enable the brakes to be more simply, easily, and perfectl y controlled, and, second, that they greatly increase the efiiciency and the certainty and reliability of operation of air-brakes as a means for controlling the movements of railroadtrains. The certain initial pressure of sixty pounds per square inch (or other maximum pressure allowed in the reservoirs) to act against the valve-piston; the substantial uniformity of the powerful reservoirpressure against the piston throughout its traverse; the presence of an emergency-reservoir always charged to its full capacity and ready for instant use; the increased brake-pressure which .results from the discharge of air from both reservoirs into the brake-cylinder when the emergency-port is opened; the ability to recharge the reservoirs while the brakes are set; the absence of any port, by-pass, or hole from that part of the inner wall of the casing which is swept by the traverse of the piston-packing, wherebyA the most efficient material can be used for such packing and whereby no avenue past the side of the piston is ever open for the ypassage of air, and the check-valve c', which guards again any possible loss of air-pressure from the reservoir K in case of any accidental sticking of the piston-particulars of certainty not heretofore attainedall combine to render the apparatus, if properly constructed and kept in repair, so absolutely certain of effective action that the responsibility for any failure of l its operation must rest with the engincer alone.

roo

As already in effect stated, the several im- ,and the auxiliary reservoir, K, not used for service-stops or grading purposes, but for applying air-pressure to the inner end ofthe pis ton, and of such capacity that its pressure is practicallyunaffected b y the movements of the piston, substantially as described, whereby the initial pressure against the inner` end of the piston is maintained substantially undiminished during the entire outward traverse thereof.

2. In an air brake system having an air-reservoir for each ear and in which the movement of the compressed air to and from the brakecylinder is governed by a sliding piston actuated by varying the ai r-pressure in the trainpipe, the combination ofthe piston and ports with a storagereservoir for ordinary service purposes and a separate reservoir for applying a practically uniform airpressnre to the inner end of the piston, substantially as described.

3. In an air brake system in which the movement of the compressed air to and from the brake-cylinder is governed by a sliding piston actuated by varying the air-pressure in the train-pipe above the normal atmospheric pressure, the combination of the piston and ports with a storage-reservoir for ordinary service purposes and an independentrescrvoir for emergency-stops, both of which are controlled by the movement of a single piston, substantially as described.

4. In an air brake system in which the movement of the compressed air to and from the brake-cylinder is governed by a sliding piston actuated by varying the air-pressure in the train-pipe above the normal atmospheric pressure, the combination of the piston with the service-reservoir and its port, all of which are controlled bythe movements of a single piston, and with an independent emergencyreservoir and ils port, substantially as described.

5. In an air brake system in which the movement of the compressed air to and from the brake-cylinder is governed by a sliding piston actuated by varying the air-pressure in the train-pipe, the combination of the piston and its ports with a storage-reservoir for ordinary service purposes, and with an independent rescrvoir or reservoirs for applying air-pressure to the inner end of the piston and for emergency stops, substantially as described.

6. In an air-brake system having an air-reservoir for each car, the combination, with the train-pipe and brake-cylinder` of two or more reservoirs under each car and a controllingvalvc and ports operated by a piston and adapted for the admission of air from either of said reservoirs at will to the brake-cylinder, substantially as described.

7. In an airbrake system having an air-reservoir for each car, the combination of two or more storage-reservoirs with a valve and its ports attached to a piston, which at different points of its traverse successively discharge their contents into the brake-cylinder, substantially as described.

8. In an air-brake system, the combination of a port-controlling piston with two storageleservoirs which, through different ports in the piston, discharge into 4the brake-cylinder at different positions of said piston, substan tially as described.

9. In an air-brake system, the combination4 of a service-reservoir and an independent res ervoir with a valve and its ports attached to a piston and so arranged that the air in the independent reservoir is applied in a substantially uniform pressure upon the piston between the limits of its traverse and is discharged into the brakecylinder at the outer end of such traverse, substantially as dcscribed.

10. In an air-brake system, the combination of two-or more storage-reservoirs with a piston and ports capable of admitting air from either of said reservoirs at will to the brakeeylinder, said piston being subject at one end to the variable air-pressure of the trainpipe and at the other end to an air-pressure which is substantially uniform between the limits of .its traverse, as herein set forth.

1l. In an air-brake system, the combination of the port-controlling piston, the train-pipe, and an independent reservoir whose contents are not subject to depletion or variation for service-stops, grading,or the governing of the piston, but are employed to furnish a uniform pressure against the inner end of the latter between the limits of its entire traverse, substantially as described.

l2. In an air-brake system in which the movement of the compressed air to and from the brake-cylinder is governed by a sliding piston actuated by varying the air-pressure in the train-pipe, the combination of the trainpipe, brake-eylindcr,carrcservoir, and a valve and its ports attached toapiston and arranged so as to open the brake-release port and discharge the brake cylinder when the piston is atan intermediate position between the extreme ends of its traverse and to close the same when at the end of its traverse, substantially as described. E' 13. In an air-brake system, the combination ofaserviee-reservoir, an emergency-reservoir, and a train-pipe and brake-cylinder with a valve and its ports attached to a piston and arranged so that it at one end of its traverse vents air from the emergency-reservoir to the brake-cylinder, at an intermediate position vents air from the service-reservoir to the brake-cylinder, and at another intermediate position discharges the air from the brakecylinder, substantially as described.

14. In an air-brake system, the combination ofthe port-controlling piston with a graduated series of springs arranged to apply yielding resistances at dierent points along its traverse corresponding to the several ports, whereby it is adapted to temporarily hold said IOO IIO

ports open or closed, substantially as de-A scribed.

15. In an air-brake system, the combination of the train-pipe, brake-cylinder, and car-reservoir with a valve and its ports attached to a piston which at one extremity of its traverse holds the dischargeport of the brake-- cylinder closed, at an intermediate position between the ends of its traverse holds said port open, and at another position admits air from a reservoir to the brake cylinder, substantially as described.

16. In an air-brake system, the combination of a service-reservoir, an emergency-reservoir, a train-pipe, and a brake-cylinder with a valve and its ports attached to, a piston which at one end of its traverse holds the brake-cylinder closed, at the other end of its traverse vents air from the emergency reservoir to the brake-cylinder, at one intermediate position vents air from the service-reservoir to the brake-cylinder, and at another intermediate position discharges air from the brake-cylinder, and a series of springs to temporarily hold the piston in its required positions for operating the intermediate service and release ports, substantially as described.

17. In an air-brake system, the combination of a port-controlling valve attached to a piston subject throughout its traverse to a substantially uniform pressure against itsinner end with a series of differential springs .acting successively against said uniform pressure, substantially as described.

18. In an air-brake system, the combination of two or more storage-reservoirs, a piston and ports capable of admitting air from either of said reservoirs at will to the brake-cylinder, and a graduated series of springs to hold the piston temporarily at different points in its traverse, substantially as described.

19. In an air-brake system, the. combination of two or more storage-reservoirs, a pistonvalve and ports capable of admitting air from either of said reservoirs at will to the brakecylinder, said piston being subject at one end to the variable air-pressure of the train-pipe and at the other end to a pressure substantially uniform throughout its traverse, and a graduated series of springs to hold the` piston temporarily at different points in its traverse, substantially as described.

20. In an air-brake system, the combination of a train-pipe, brake-cylinder, air-reservoir, and ports connecting the same with a valve controlling said ports and operated by a piston so arranged as to discharge the brakecylinder at a position intermediate between the eXtreme ends of the traverse of the piston, with a spring or weight arranged to co-operate in the restoration of the piston to its normal position at the end of its traverse when the pressure is increased in the train-pipe, whereby this restoration 'may be effected without reu leasing the brakes, substantially as described.

intermediate between the extreme ends of its traverseopens the release-port to discharge the brake-cylinder and release the brakes with a resistance-spring arrangedto temporarily arrest the movement ofthe piston at the point Where it opens said release-port, subitantially as described. l

22. In an air-brake system, the combination of separate service and emergency reservoirs on each car, and ports with a piston and valve governing said ports, and a resistancespring adapted to temporarily arrest the movement of the piston at the point where it opens the service-port, substantially as described.

23. In an air-brake system, the combination of a service-reservoir, a piston whose inner end is subject to a substantially uniform pressure between the limits of its traverse, a releaseport opened by the piston at an intermediate point in its traverse, and a spring to tempo-- raril y arrest the movement of the piston at the point where it opens said release-port, substantially as described.

24. In an air-brakesystem, the combination of a service reservoir, a piston whose inner end is subject to a substantially uniform pressure between the limits of its traverse, and a re sistance-spri ng to arrest the piston at the service-port from the service -reservoir to the brake-cylinder and enable the latter to be held open or closed at will, substantially as described.

25. In an air-brake system, the combination of a train pipe, brake-cylinder, and car-reservoir and ports connecting the same, and a valve controlling the ports and attached to a. piston with two or more springs which apply their resistance to the piston in the same direction, and which, as the piston moves in its traverse, come successively into action, substantially as described.

26. In an air-brake system, the combination of a train-pipe, brake-cylinder, and car-reservoir and ports connecting the same, and a valve controlling the ports and attached to a piston operating underasu'bslantially uniform pressure upon its inner end, with two or more springs which come successively into action against its outer end to resist said pressure, substantially as described.

' of a port-controlling piston which at a position IOO IIO

27. In an air-brake system, the combination of the piston and ports, spring S or weight, the

arranged to operate substantially as described.

28. In an air-brake system in which the piston releases the brakes when at an intermediate posit-ion between the eXtreme ends of its traverse, the combination of the cock m with the separate open-air port M and the normal open-air port M, whereby the piston may be enabled to release the brakes when at the inner end of its traverse or when in said intermediate position, substantially as described.

29. In an air-brake system, the combination of a port-controlling piston with an open-air port, M, wl1ich,\vhen unobstructed, causes the brakes to be released when the piston is at a' 3l. In an airibrake system, the combination of @train-pipe, brakecylinder, anreservoir, and ports connecting themsame, and a valve controlling the ports and operated by a piston, with two slides and two springs acting, respectively, upon said slides, and arranged so that the piston in its movement successively encounters the resistance otsaid springs, substantially as described.

THERON S. E. DIXON.

Witnesses:

L. HrLL, WM. ML HILL. 

